An octogenarian who shot and injured a teenager who rang the wrong doorbell in Kansas City, Mo., pleaded guilty on Friday to second-degree assault, resolving the case just days before a trial was set to begin.

The man, Andrew D. Lester, 86, had been charged with first-degree assault and armed criminal action in the April 2023 shooting of Ralph Yarl, a high school student who arrived at the wrong house — Mr. Lester’s — while trying to pick up his younger brothers. It was uncertain what sentence Mr. Lester will face after pleading guilty to a less serious charge of second-degree assault

The shooting of Mr. Yarl led to protests in Kansas City and a national outcry, including an invitation by former President Joseph R. Biden Jr. for the teenager to visit the White House. It also raised painful questions about race in Kansas City, which has a long history of segregation. Many residents and politicians in the area said they believed that race played a role in the shooting, while the county prosecutor said early on that “there was a racial component to the case.” Mr. Lester is white and Mr. Yarl is Black.

Mr. Lester, who could have been sentenced to life in prison if convicted at trial on the most serious charge he faced, did not dispute shooting Mr. Yarl, who was 16 years old at the time. But months ago, he had pleaded not guilty, and his lawyer had indicated that he would claim self-defense at trial, which was set to begin next week.

Mr. Yarl was seated in the front row of the courtroom during the hearing on Friday. His mother, Cleo Nagbe, issued a statement after Mr. Lester entered his plea.

“While this marks a step toward accountability, true justice requires consequences that reflect the severity of his actions — anything less would be a failure to recognize the harm he has caused,” Ms. Nagbe said. She added, “We remain hopeful that his sentencing will not be merely a slap on the wrist but a decision that upholds the seriousness of his crime.”